Abstract - Hydrologic Study of Jewel Cave/Wind Cave. Final Report.
Alexander, E. Calvin, Jr., Davis, Marsha A. and Alexander, Scott C.. 1989. Hydrologic Study of Jewel Cave/Wind Cave. Final Report. Contract: CX-1200-S-A047 (U of Minn. 0645-5647). 196 p.
Jewel and Wind Caves, the second and third longest caves in the United States, are part of the karst region of the Black Hills of South Dakota. The karst system of the Black Hills, primarily comprising the Pahasapa Limestone, is the recharge zone for the regionally important Madison aquifer. Dye tracing and chemical analysis of karst waters were used at Wind and Jewel Cave to better understand the surface to subsurface hydrologic relationships and human impact on these caves. Through the course of this study the area of concern extended beyond the Park's and Monument's boundaries simply because groundwater flow is unrelated to human defined boundaries. Rhodamine WT and fluorescein dye traces conducted at both caves have demonstrated direct hydrologic connections between the surface development and the underlying caves. Dye traced from the Jewel Cave sewage line and from the parking lot at both caves appeared in sporadic, short dye pulses in the caves within a few days of dye imput. The continued discovery of dye, up to three years after imput, indicates that any contaminant spilled over these caves will be present in the system for many years. This pattern of behavior observed at Wind and Jewel Caves may be consistent for the karst system of the Black Hills. A successful trace of the sink of Beaver Creek to the Wind Cave water supply well demostrates the potential impact of surface activities on the National Park's water supply. Water samples collected from drips and pools in Wind and Jewel Caves have been analyzed for temperature, pH, and major and minor dissolved species. A wide range of chemical compositions have been found. The Mg/Ca molar ratios in Jewel Cave are often greater than 1, while the Mg/Ca values at Wind Cave are usually less than 1. It is suggested that the source of these Mg-rich waters is related to evapotranspiration processes in the uppermost area of infiltration. Elevated levels of chlorine, sodium, and nitrate are sporadically present in the water of both caves beneath surface structures and appear to be indicative of surface pollution. As part of this hydrologic investigation we conducted studies that included the mapping of and the collection of chemical and isotropic analyses of thermal waters from springs and wells of the southern Black Hills karst. Many springs form complex resurgences in which waters with different chemistries and temperatures emerge in the same areas. Three separate components appear to be present: waters that have dissolved only calcite and dolomite, waters which have dissolved large amounts of calcium sulfate and gained magnesium presumably via dedolomitization reactions, and waters containing sodium chloride. Both the chemical and isotopic data indicate that the water's warmth comes from radiogenic heat production and/or enhanced local heat flow -- not from chemical heat sources or a hypothetical local magma body. Contract CX-1200-5-A047, May 1, 1985 to April 30, 1988.
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